Merge pull request #98 from tsawler/development

Add check for Content-Type header; simplify error checking; improve t…

tools.go

@@ -44,6 +44,16 @@ type XMLResponse struct {
 
 // ReadJSON tries to read the body of a request and converts it from JSON to a variable.
 func (t *Tools) ReadJSON(w http.ResponseWriter, r *http.Request, data interface{}) error {
+
+	// check content-type header; it should be application/json. If it's not specified, try to decode the body anyway.
+	if r.Header.Get("Content-Type") != "" {
+		contentType := r.Header.Get("Content-Type")
+		if strings.ToLower(contentType) != "application/json" {
+			return errors.New("the Content-Type header is not application/json")
+		}
+	}
+
+	// set a sensible default for the maximum payload size.
 	maxBytes := 1024 * 1024 // one megabyte
 
 	// if MaxJSONSize is set, use that value instead of default.
@@ -75,10 +85,7 @@ func (t *Tools) ReadJSON(w http.ResponseWriter, r *http.Request, data interface{
 			return errors.New("body contains badly-formed JSON")
 
 		case errors.As(err, &unmarshalTypeError):
-			if unmarshalTypeError.Field != "" {
-				return fmt.Errorf("body contains incorrect JSON type for field %q", unmarshalTypeError.Field)
-			}
-			return fmt.Errorf("body contains incorrect JSON type (at character %d)", unmarshalTypeError.Offset)
+			return fmt.Errorf("body contains incorrect JSON type for field %q at offset %d", unmarshalTypeError.Field, unmarshalTypeError.Offset)
 
 		case errors.Is(err, io.EOF):
 			return errors.New("body must not be empty")

tools_test.go

@@ -87,6 +87,7 @@ var jsonTests = []struct {
 	errorExpected bool
 	maxSize       int
 	allowUnknown  bool
+	contentType   string
 }{
 	{name: "good json", json: `{"foo": "bar"}`, errorExpected: false, maxSize: 1024, allowUnknown: false},
 	{name: "badly formatted json", json: `{"foo":"}`, errorExpected: true, maxSize: 1024, allowUnknown: false},
@@ -101,6 +102,7 @@ var jsonTests = []struct {
 	{name: "missing field name", json: `{jack: "bar"}`, errorExpected: true, maxSize: 1024, allowUnknown: false},
 	{name: "file too large", json: `{"foo": "bar"}`, errorExpected: true, maxSize: 5, allowUnknown: false},
 	{name: "not json", json: `Hello, world`, errorExpected: true, maxSize: 1024, allowUnknown: false},
+	{name: "wrong header", json: `{"foo": "bar"}`, errorExpected: true, maxSize: 1024, allowUnknown: false, contentType: "application/xml"},
 }
 
 func TestTools_ReadJSON(t *testing.T) {
@@ -114,15 +116,19 @@ func TestTools_ReadJSON(t *testing.T) {
 
 		// declare a variable to read the decoded json into.
 		var decodedJSON struct {
-			Foo  string   `json:"foo"`
-			Chan chan int `json:"chan"`
+			Foo string `json:"foo"`
 		}
 
 		// create a request with the body.
 		req, err := http.NewRequest("POST", "/", bytes.NewReader([]byte(e.json)))
 		if err != nil {
 			t.Log("Error", err)
 		}
+		if e.contentType != "" {
+			req.Header.Add("Content-Type", e.contentType)
+		} else {
+			req.Header.Add("Content-Type", "application/json")
+		}
 
 		// create a test response recorder, which satisfies the requirements
 		// for a ResponseWriter.